Such electromotorically driven centrifugal pumps, with which the rotor of the electric motor is separated from the stator by a can, in a multitude of construction variants, in particular for pump assemblies of a smaller or medium power, in many varieties, are counted as belonging to the state of the art. Thereby, the can which can be designed as a canned pot, on the one hand serves for the sealing of the stator with respect to the pump liquid, and on the other hand for receiving one or two bearings, with which the rotor is rotatably mounted. With such types of canned pumps, the rotor comprises a shaft which typically on the motor-side end of the can as well as in the region of a bearing plate arranged in the region between the pump and the motor, is rotatably mounted, and at its end distant to the motor is connected to an impeller, or, several impellers with multi-stage centrifugal pumps.
Thereby, with regard to centrifugal pumps, as are applied as heating circulation pumps for example, is counted as belonging to the state of the art, to design the can together with the bearing plate as one piece as a deep-drawn part in the form of a canned pot which is manufactured from stainless steel for example. Such canned pots have proven their worth in practice and are applied in a particularly advantageous manner in combination with asynchronous motors.
However, permanent magnet motors are better with regard to efficiency, with which metallic cans however are disadvantageous since they entail eddy current losses.
It is also counted as belonging to the state of the art, to apply a can between the rotor and the stator, in which can the rotor runs and which close to its ends in each case via a seal is sealed on the one hand with respect to the stator and on the other hand with respect to the bearing plate. Such a sealing on both sides however on the one hand requires quite some effort with regard to design and on the other hand is prone to disturbance and wear.